Air foil bearing

Abstract

Air foil bearing capable of adjusting stiffness of single bumps by varying widths of the single bumps. Since the bumps have the same height in an initial stage, a wedging effect is implemented only when a load is applied thereto by an oil film. Therefore, the air foil bearing is advantageous in terms of height management thereof. In addition, it is possible to stably dampen shocks applied in the direction of rotation of a rotor, to improve a support capability, and to reduce shocks due to damping. Therefore, it is possible to enhance durability of the air foil bearing.

What is claimed is: 
     
       1. An air foil bearing for rotatably supporting a rotary shaft, comprising:
 a disc-shaped plate, a plurality of bump foils coupled to the plate, and a top foil disposed above each of the bump foils while one end of the top foil is coupled to the plate and the other end thereof is a free end, 
 wherein each of the bump foils comprises first to fourth foils extending from the coupled ends in a direction opposite to a direction of rotation of a rotor, 
 wherein ends of the first to fourth foils are connected as one piece, and 
 wherein a leading ridge (A) of each of the first to fourth foils, which is adjacent to the free end, has a height different from another adjacent bump ridge. 
 
     
     
       2. The air foil bearing according to  claim 1 , wherein the height of the leading ridge (A) of each of the first to fourth foils is lower than the height of another adjacent bump ridge in the direction of rotation of a rotor. 
     
     
       3. The air foil bearing according to  claim 2 , wherein the height of the leading ridge (A) of each of the first to fourth foils is set to be within 70% of the height of another adjacent bump ridge in the direction of rotation of a rotor. 
     
     
       4. The air foil bearing according to  claim 3 , wherein the top foil has an inclined section (L 1 ) in which a gap between the top foil and the plate is gradually increased, and a flat section (L 2 ) in which the gap therebetween is constant. 
     
     
       5. The air foil bearing according to  claim 4 , wherein the leading ridge (A) of each of the first to fourth foils corresponds to a starting position of the flat section (L 2 ) of the top foil. 
     
     
       6. The air foil bearing according to  claim 3 , wherein an end (B) adjacent to the leading ridge (A) of each of the first to fourth foils is coupled to the plate by spot welding. 
     
     
       7. The air foil bearing according to  claim 1 , wherein the bump foil is divided into first to fourth foils by a plurality of slits. 
     
     
       8. The air foil bearing according to  claim 7 , wherein stiffness of the first to fourth foils is adjusted according to a width of each of the slits and a bump width of the bump foil. 
     
     
       9. The air foil bearing according to  claim 8 , wherein some of the first to fourth foils have different bump widths from one end thereof to the other end thereof. 
     
     
       10. The air foil bearing according to  claim 7 , wherein the plurality of slits have different shapes. 
     
     
       11. The air foil bearing according to  claim 7 , wherein the bump foil further comprises a trailing edge connecting the first foil to the second foil. 
     
     
       12. An air foil bearing for rotatably supporting a rotary shaft, comprising:
 a disc-shaped plate, a plurality of bump foils coupled to the plate, and a top foil disposed above each of the bump foils while one end of the top foil is coupled to the plate and the other end thereof is a free end, 
 wherein each of the bump foils comprises first to fourth foils extending from the coupled ends in a direction opposite to a direction of rotation of a rotor 
 wherein the bump foil is divided into first to fourth foils by a plurality of slits, 
 wherein the bump foil further comprises a trailing edge connecting the first foil to the second foil, and 
 wherein a distance (D) from an end of each of the slits to the trailing edge (F) is less than or equal to twice a bump pitch (C).